In the electronics field a variety of techniques have been employed to terminate electrical cables. Such cables may have one or more electrical conductors covered or separated by electrical insulation. Typically an electrical connector (cable termination) is coupled to the end of such a cable to form a cable termination assembly which facilitates connecting the one or more conductors of the cable to other cables, terminal boards, modular equipment used in computers, etc. Important features of such cable termination assemblies are facility of manufacture and/or use, mechanical strength, security and integrity of electrical connections made therein and thereby, cost efficiency, etc.
Multiconductor electrical cables have enjoyed widespread use in the electronics industry. One such multiconductor cable includes plural wires, each including a conductor covered by its own insulation, bundled together mechanically, e.g. by a fastener, external sheath, or the like. Another such multiconductor cable includes plural electrical conductors contained in and electrically isolated from each other by electrical insulation as an integral structure. Flat or ribbon cable is a particular version of this latter multiconductor cable. The insulation for such ribbon cable may be of various electrically non-conductive materials, such as plastic or plastic-like materials, polytetrafluoroethylene (e.g. Teflon), fibreglass, or like materials. Typical flat ribbon cables may have multiple conductors therein numbering more than eighty.
In some uses of ribbon cable, such as for high speed signal transmission purposes, it may be desirable electrically to isolate adjacent signal carrying conductors (hereinafter signal conductors, although some also may be connected to a reference potential, e.g. ground), for example by providing one or more conductors (hereinafter ground or isolating conductors) therebetween that are maintained at a reference potential, such as ground potential. Such electrical isolation is commonly referred to as ground isolation, it being appreciated that the reference potential may be other than ground potential, and may be achieved, for example, by connecting alternate conductors of the cable to a ground reference potential. Moreover, for high speed signal transmission purposes it has been found that woven ribbon cable and cables having Teflon or like insulation usually are most desirable.
In one prior technique for terminating a ribbon cable, the latter, a plurality of electrical contacts, and several non-conductive body parts are placed in a jig press and are secured together mechanically to form a cable termination assembly. Another technique for terminating multiconductor cables disclosed in U.S. Pat. No. 4,030,799 provides for direct penetration of electrical contacts through the cable insulation to connect with respective conductors therein and a body of dielectric material molded directly about at least part of the contacts and cable to secure the same as an integral structure. There should be adequate spacing of the conductors so that the contacts piercing the cable preferably only engage a single conductor therein.
In the past, to obtain ground isolation for such multiconductor ribbon cables the ground conductors were connected to respective contacts of the cable termination assembly, and each of these contacts were in turn connected to an external ground. Therefore, usually less than half of the remaining contacts of the cable termination assembly, i.e. those coupled to the respective signal carrying conductors, were actually available to carry useful signals. However, in U.S. Pat. No. 4,094,564 is disclosed a multiple conductor cable termination assembly in which, for example, effective ground isolation is provided the signal carrying conductors of a multiconductor cable while making efficient use of the contacts of the connector for signal connection purposes. In such assembly an electrically conductive bus electrically connects selected conductors of the multiconductor cable in common with each other and also, if desired, with one or more contacts of the connector so that all of such commonly connected conductors are at a common reference potential, such as ground potential. The majority of the contacts, then, may be used for electrical connection of signal carrying conductors of the multiconductor cable to an external device. A strain relief mechanism, which prevents force applied to the cable termination assembly tending to separate the termination from the cable from detrimentally affecting the integrity of the connections between respective conductors and contacts is disclosed in U.S. Pat. No. 4,094,564. Such mechanism is of the molded type in which the cable extends out of a strain relief body, which is molded directly about part of the cable, in a direction that is angularly displaced from the insertion and withdrawal direction of the connector contacts. Therefore, a force tending to separate the cable from the termination would be dissipated in the molded strain relief body without detrimentally affecting the connections between respective conductors and contacts, which also preferably are encased within the molded strain relief body. The angular exit of the cable from the strain relief body facilitates close packing of plural similar cable termination assemblies.
To facilitate removing electrical connectors from connection with external devices, pull tabs have been used. Such pull tabs generally permit applying a withdrawing force from a cable termination assembly without directly pulling on the cable itself.